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Fig. 4
Silencing mechanosensory neurons decreases speed of locomotion.
(A) In vivo fluorescence image and (B) immunohistochemistry for GFP in 4 dpf Tg(isl2b:gal4,cmlc2:eGFP;UAS:GFP-aequorin-opt) double transgenic zebrafish larva show selective expression of GFP-aequorin in mechanosensory neurons: trigeminal ganglia (arrow), Rohon-Beard spinal neurons and their ascending axons (arrowhead) and dorsal root ganglia (*), but no expression in muscle fibers (n = 4). (C–D) Superimposed images from the raw high-speed camera recording (left), the corresponding automated tracking (middle, pink triangles represent the head and green lines the tail of the fish) and tail angle over time extracted from the tracking analysis (right; stimulus is represented by the black vertical line, duration of the event is the black horizontal line) of a typical escape elicited by an acoustic stimulus in a freely-swimming control sibling larva at 6 dpf (C), and in a Tg(isl2b:gal4,cmlc2:eGFP;UAS:BoTxBLC-GFP) larva (D). (E1) Distance travelled was unchanged in BoTxBLC+ and control larvae (10.2 ± 0.2 mm versus 10.6 ± 0.2 mm, p=0.1). (E2) Number of oscillations was unchanged in BoTxBLC+ and control larvae (6.0 ± 0.2 versus n = 6.1 + /- 0.2 oscillations, p=0.6). (E3) BoTxBLC+ larvae showed a decreased tail-beat frequency (TBF, 34.2 ± 0.4 Hz versus 37.8 ± 0.3 Hz, p<0.001). (E4) BoTxBLC+ larvae showed a decreased speed of escape responses (56.9 ± 1.1 versus 64.1 ± 0.9 mm/s, p<0.001). (E5) Escape duration was increased in BoTxBLC+ larvae compared to control siblings (182.0 ± 3.0 ms versus 168.1 ± 2.4 ms, p<0.001). (For all parameters: control group: n = 176 larvae from 8 clutches, n = 561 escapes; BoTxBLC+ group: n = 128 larvae from 8 clutches, n = 329 escapes).